Minimax recursive with max/min values

gistfile1.txt

def minimax_back(max_player = true, ply = 0, min_score = 1000, max_score = -1000)                                                                                              
  if board.winner?
    return(max_player ? (-1000 + ply) : (1000 - ply))
  elsif board.draw_game?
    return 0
  end 

  if ply >= max_ply
    return(max_player ? max_score : min_score)
  end 
  best_move = 0 
  score = 0 
  available_moves.each do |index|
    board[][index] = ( max_player ? side : opposite_side(side) )
    score          = minimax(!max_player, ply + 1, min_score, max_score)
    undo_move(index)

    if max_player && score > max_score
      max_score  = score
      best_move  = index
    elsif !max_player && score < min_score && min_score.abs > max_score
      min_score  = score
    end 
    break if max_min_swapped?(max_score, min_score)
  end 

  return( ply == 0 ? best_move : ( max_player ? max_score : min_score ) ) 
end 

def set_max_ply(moves)
  5   
end 

def max_min_swapped?(max, min)
  max >= min 
end